Designing a Mash Tun
Online research yields countless mash tun designs; most are kettle-or cooler-based with a means to filter the sweet wort.
Think about tun sizing. You want one big enough to do any beer that your heart desires. Choose a tun that's too small and the fun, high-octane beers require extract to achieve. Conversely, choose a too-large tun and suffer unstable rests and shallow grain beds.
Cooler tuns, based on ten-gallon rounds or 40- to 100-quart rectangular coolers, are a breeze to use. Add some hot water to heat the mash tun, toss, add your water and grain, and close for an hour. Many tuns hold temperature perfectly
Add a spigot by punching out the plastic drainage valve and securing a ball valve and bulk head on either side. Some even skip the valve and feed a tight-fitting hose or stopper and pipe through the hole. You can attach any wort-draining rig inside.
The tun's disadvantage is a lack of direct heating. No problem for single-infusion mashes, but to change temperatures you need alternate heating means.
Adding heat is no problem for a mash tun built on a kettle. Just turn on the flame and stir continuously until you're a few degrees under your target. The carryover heat coasts to the right temperature.
Conversely, heat loss is experienced in a kettle. To mitigate the precipitous drop in mash temperature, wrap the kettle with a blanket. Remember to remove it before firing the burner.
To make a kettle tun, you must drill or cut a hole for a valve. With weldless kits, you can screw things together, but for a sturdy, leakproof setup, you'll need experience (or a friend who has experience) with stainless steel welding equipment.
It is imperative that you clean a tun shortly after the brew session. The smell of old mash left stewing in the tun is horrendous and almost impossible to remove from a cooler.
Now that you can mash, you need to separate your new wort from the spent grains. In extract brewing you could pour the grain in a fine-mesh strainer, but it's no longer practical. Instead, brewers focus on straining devices at the bottom of the mash tun. These gizmos and the barley husks combine to create escape routes for the precious liquid.
False bottom — A false bottom covers the floor of the tun and the drainage valve. Perforations allow the liquid to flow out of the tun. To prevent scorching on the kettle floor, direct heating is discouraged. When preparing water for mashing, you have to add extra “foundation” water to bring the level to the false bottom.
Manifold — An easy-to-construct alternative is the wort manifold. Built of copper pipes or PVC (for coolers only), manifolds separate wort via a series of drilled holes or slots that face the bottom of the mash tun. The wort flows up into the pipe and out the spigot. Use a ring or rectangular configuration of pipes spaced an inch or so apart to ensure equal drainage from all parts of the mash.
Steel braid — Even easier to construct are stainless steel hose braids which can be found wrapped around rubber water hosing. To create a mash filter, discard the rubber hose, flatten one end, and fold over like a toothpaste tube. With a pair of pliers, crimp the folded end and attach to your spigot. Inserting a length of copper pipe prevents the braid from squashing. With a braid, you must be careful not to damage it by overzealous mash stirring.
When buying a braid, make sure you buy a steel braid. Manufacturers these days are making nylon-braided hoses painted to look like metal.